1. Field of the Invention
The present invention relates to a method of processing an image by way of gradation conversion or color correction.
2. Description of the Related Art
In the printing and platemaking fields, there have widely been used image reading, recording, and reproducing systems for electrically processing a color image recorded on a subject to be read, producing film plates or printing plates in the colors C, M, Y, K, and obtaining a desired print from the film plates or printing plates for the purposes of making printing and platemaking processes more efficient and improving the image quality.
The color image is read by a scanner device or the like and then converted in gradation or corrected in color for each of the colors C, M, Y, K in order to obtain a print in a desired gradation or color tone with respect to an attentional portion.
Specifically, the gradation converting process converts the density of the color image into a density capable of achieving a desired output halftone dot %. A tone curve, which is an input-density vs. output-density conversion table, used in the gradation converting process is adjusted in highlight (HL), shadow (SD), and middle (MD) portions of the color image according to a gradation corrective coefficient that the operator has established. However, the tone curve is adjusted by correcting gradation corrective functions prepared respectively for the HL, SD, and MD portions based on the gradation corrective coefficient. Consequently, if a certain gradation between the HL and MD portions is finely adjusted, then the gradation of an unintended portion is also varied.
In the color correcting process, it is customary to prepare corrective intensity functions primarily for the six hues of C, M, Y, R, G, B and correct the corrective intensity functions using a color corrective coefficient established by the operator for thereby obtaining a desired color tone. For adjusting the color tone of a particular portion, since the corrective intensity functions are set primarily for the six hues of C, M, Y, R, G, B, the color tone of an unintended portion is also varied. For example, if a flesh color is to be adjusted, then since the corrective intensity functions primarily for the hues of R and Y are corrected, the hues of R and Y are largely changed rather than the flesh color itself. If a duller green is to be adjusted, then since a corrective intensity function is corrected more greatly for a color of greater saturation, a more vivid green is changed rather than the duller green.